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A series of fluorescent sensor molecules based on a phosphane sulfide derivative were designed and synthesized. The effect of the distance between the complex entities as well as the number and the length of fluorophores was investigated using both steady-state and time-resolved fluorescence methods. The complexation behavior of these sensor molecules, which have a distinct affinity for Hg(2+), is reported. The coordination of Hg(2+) induces a photoinduced electron transfer from fluorophore to the complexed mercury and results in a significant decrease of the fluorescence. Theses sensors exhibit very low detection limits in CH(3)CN/H(2)O (80/20 v:v) and excellent sensitivity to Hg(2+) over other potentially interfering cations such as Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ag(+), Zn(2+), Cd(2+) and Pb(2+).

A series of fluorescent phosphane oxide derivatives based on diphenylphosphanoethane (DPPE) and diphenylphosphanomethane (DPPM) skeletons has been prepared by means of Grignard reactions and Sonogashira cross-couplings. The photophysical properties and the linear and nonlinear spectra of these compounds have been investigated. An edge-to-face conformation resulting in the formation of an excimer was confirmed by fluorescence lifetime measurements of these multichromophoric derivatives. Upon complexation with heavy metal ions such as Pb2+ and Cd2+, a red shift of the one- and two-photon excitation spectra was observed in the absorption and emission spectra. Furthermore, enhancement of the electron-withdrawing character of the phosphane oxide resulted in a significant enhancement of the two-photon absorption cross-section, leading to the first biphotonic Cd2+ sensors combining high affinity for Cd2+, large two-photon absorption cross-sections, and significant enhancement of the two-photon excited fluorescence in the presence of the cation. Such derivatives are highly promising for incorporation into devices for the detection of heavy metal ions in water and effluents.

A new fluorescent molecular sensor for Hg2+ based on the phosphane sulfide derivative exhibits a very low detection limit in an aqueous medium (3.8 nM) with a very high selectivity over other interfering cations. The reversibility of the complexation process was also examined and was found to be successful. [structure: see text]